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Commit 278ce05b authored by Cary Clark's avatar Cary Clark
Browse files

accelerate consecutive flings 

Use the fact that the scroller keeps track of the current velocity
to accelerate subsequent flings. The current velocity is added to
the new velocity if the flings are in the same general direction
and if the fling animation hasn't been aborted.

This makes it easier to move to the top or bottom of very large
pages (either in overview mode or reading mode) by taking
consecutive flings as a cue from the user that they want to
page faster. The user can stop the fling with any action as
before.

fixes http://b/issue?id=2066090
parent 05c9ed9c

core/java/android/webkit/WebView.java

+39 −4
Original line number Diff line number Diff line
@@ -342,6 +342,9 @@ public class WebView extends AbsoluteLayout 
     */

    VelocityTracker mVelocityTracker;

    private int mMaximumFling;

    private float mLastVelocity;

    private float mLastVelX;

    private float mLastVelY;



    // use this flag to control whether enabling the new double tap zoom

    static final boolean ENABLE_DOUBLETAP_ZOOM = true;
@@ -1795,6 +1798,13 @@ public class WebView extends AbsoluteLayout 
                , contentToView(x.right), contentToView(x.bottom));

    }



    // stop the scroll animation, and don't let a subsequent fling add

    // to the existing velocity

    private void abortAnimation() {

        mScroller.abortAnimation();

        mLastVelocity = 0;

    }



    /* call from webcoreview.draw(), so we're still executing in the UI thread

    */

    private void recordNewContentSize(int w, int h, boolean updateLayout) {
@@ -1819,7 +1829,7 @@ public class WebView extends AbsoluteLayout 
                mScrollY = pinLocY(mScrollY);

                // android.util.Log.d("skia", "recordNewContentSize -

                // abortAnimation");

                mScroller.abortAnimation(); // just in case

                abortAnimation(); // just in case

                if (oldX != mScrollX || oldY != mScrollY) {

                    sendOurVisibleRect();

                }
@@ -2339,7 +2349,7 @@ public class WebView extends AbsoluteLayout 
                    animationDuration > 0 ? animationDuration : computeDuration(dx, dy));

            invalidate();

        } else {

            mScroller.abortAnimation(); // just in case

            abortAnimation(); // just in case

            scrollTo(x, y);

        }

        return true;
@@ -2963,7 +2973,7 @@ public class WebView extends AbsoluteLayout 
        mLastTouchX = halfW;

        int halfH = height >> 1;

        mLastTouchY = halfH;

        mScroller.abortAnimation();

        abortAnimation();

        mZoomScrollStart = System.currentTimeMillis();

        Rect zoomFrame = scrollZoomFrame(width, height

                , scrollZoomMagScale(mZoomScrollInvLimit));
@@ -3850,6 +3860,9 @@ public class WebView extends AbsoluteLayout 
                    mLastScrollY = mZoomScrollY;

                    // If two taps are close, ignore the first tap

                } else if (!mScroller.isFinished()) {

                    // stop the current scroll animation, but if this is

                    // the start of a fling, allow it to add to the current

                    // fling's velocity

                    mScroller.abortAnimation();

                    mTouchMode = TOUCH_DRAG_START_MODE;

                    mPrivateHandler.removeMessages(RESUME_WEBCORE_UPDATE);
@@ -4110,6 +4123,7 @@ public class WebView extends AbsoluteLayout 
                            doFling();

                            break;

                        }

                        mLastVelocity = 0;

                        WebViewCore.resumeUpdate(mWebViewCore);

                        break;

                    case TOUCH_DRAG_START_MODE:
@@ -4475,6 +4489,27 @@ public class WebView extends AbsoluteLayout 
            vx = vx * 3 / 4;

            vy = vy * 3 / 4;

        }

        float currentVelocity = mScroller.getCurrVelocity();

        if (mLastVelocity > 0 && currentVelocity > 0) {

            float deltaR = (float) (Math.abs(Math.atan2(mLastVelY, mLastVelX)

                    - Math.atan2(vy, vx)));

            final float circle = (float) (Math.PI) * 2.0f;

            if (deltaR > circle * 0.9f || deltaR < circle * 0.1f) {

                vx += currentVelocity * mLastVelX / mLastVelocity;

                vy += currentVelocity * mLastVelY / mLastVelocity;

                if (DebugFlags.WEB_VIEW) {

                    Log.v(LOGTAG, "doFling vx= " + vx + " vy=" + vy);

                }

            } else if (DebugFlags.WEB_VIEW) {

                Log.v(LOGTAG, "doFling missed " + deltaR / circle);

            }

        } else if (DebugFlags.WEB_VIEW) {

            Log.v(LOGTAG, "doFling start last=" + mLastVelocity

                    + " current=" + currentVelocity);

        }

        mLastVelX = vx;

        mLastVelY = vy;

        mLastVelocity = (float) Math.hypot(vx, vy);



        mScroller.fling(mScrollX, mScrollY, -vx, -vy, 0, maxX, 0, maxY);

        // TODO: duration is calculated based on velocity, if the range is
@@ -4683,7 +4718,7 @@ public class WebView extends AbsoluteLayout 
        mLastTouchY = y + (float) (mWebTextView.getTop() - mScrollY);

        mLastTouchTime = eventTime;

        if (!mScroller.isFinished()) {

            mScroller.abortAnimation();

            abortAnimation();

            mPrivateHandler.removeMessages(RESUME_WEBCORE_UPDATE);

        }

        mSnapScrollMode = SNAP_NONE;

core/java/android/widget/Scroller.java

+11 −0
Original line number Diff line number Diff line
@@ -132,6 +132,17 @@ public class Scroller { 
        return mCurrY;

    }

    

    /**

     * @hide

     * Returns the current velocity.

     *

     * @return The original velocity less the deceleration. Result may be

     * negative.

     */

    public float getCurrVelocity() {

        return mVelocity - mDeceleration * timePassed() / 2000.0f;

    }



    /**

     * Returns the start X offset in the scroll. 

     *